1. Technical Field
This invention relates to sensor probes used in the process analytical industry, and more particularly to a retractable assembly for enabling adjustable insertion and retraction of electrochemical sensors to and from a fluid process without requiring shut-down of the process.
2. Background Information
Retractable insertion assemblies are used in the process analytical industry to enable insertion and retraction of sensor probes under process pressure and temperature conditions without leakage of process fluid. Retraction may be carried out in order to replace or perform maintenance or calibration of probes.
Insertion assemblies for conventional 12 mm diameter pH sensors typically have two positions—inserted and retracted. During insertion/retraction, the sensor probe is placed within a central shaft of the insertion assembly. This central shaft is axially slidable between the two positions. A pair of o-rings may be placed around the central shaft to provide a fluid-tight seal that helps prevent leakage of the process fluid in both positions and as the shaft moves between the inserted and retracted positions. The inserted and retracted positions are secured by conventional quarter-turn fasteners, e.g., by pins that are engaged upon a quarter turn of the shaft.
This approach may perform satisfactorily when used with probes having a specific fixed length and fixed insertion depth in the process fluid. However, this approach is not intended to accommodate probes of varying length and/or applications involving variable depths of insertion into the process.
A need therefore exists for an improved insertion assembly that addresses one of more of the foregoing issues associated with conventional approaches.